make feather can ack example work with stm32f405

FeatherCAN_CircuitPython/listener-ack/code.py

@@ -50,5 +50,5 @@ while True:
     if gap != 1:
         print(f"gap: {gap}")
 
-    print("Sending ACK")
+    print(f"Sending ACK: {count}")
     can.send(canio.Message(id=0x409, data=struct.pack("<I", count)))

FeatherCAN_CircuitPython/sender-ack/code.py

@@ -38,14 +38,14 @@ while True:
     print(f"Sending message: count={count} now_ms={now_ms}")
 
     message = canio.Message(id=0x408, data=struct.pack("<II", count, now_ms))
+
+    # Keep trying to send the same message until confirmed.
     while True:
+        received_ack_confirmed = False
         can.send(message)
 
-        message_in = listener.receive()
-        if message_in is None:
-            print("No ACK received within timeout")
-            continue
-
+        # Read in all messages.
+        for message_in in listener:
             data = message_in.data
             if len(data) != 4:
                 print(f"Unusual message length {len(data)}")
@@ -53,9 +53,16 @@ while True:
 
             ack_count = struct.unpack("<I", data)[0]
             if ack_count == count:
-            print("Received ACK")
+                print(f"Received ACK: {ack_count}")
+                received_ack_confirmed = True
                 break
+            else:
                 print(f"Received incorrect ACK: {ack_count} should be {count}")
 
+        if received_ack_confirmed:
+            break
+
+        print(f"No ACK received within receive timeout, sending {count} again")
+
     time.sleep(.5)
     count += 1